1. Field of the Invention
The invention relates to a device and a method for feeding a material layer onto a construction platform, or onto at least one material layer located on the construction platform, for producing an object in the course of a generative production method, which is mounted so it is linearly movable relative to a material reservoir and the construction platform along a motion plane, to which the material reservoir and the construction platform can be orthogonally deflected.
2. Description of the Prior Art
Generative manufacturing methods have already been used successfully for many years to produce three-dimensional objects, which are produced in the course of iterative joining of layer or volume elements onto or to one another. Manifold different materials are available as starting materials, which can be provided both in powder or granule form or also in the form of fluids, for example, as suspensions.
In addition to generative lamination and extruding technologies, which are also known under the name laminated object manufacturing (LOM) or fused deposition modeling (FDM), the further observations relate to generative production methods in which a plurality of individual material layers are deposited successively on a construction platform, which can preferably be lowered vertically, to form a three-dimensional object with the material layers being individually subjected to a local selective solidification process. Reference is made to FIG. 2 for the illustration of such a production method, which shows a schematic view of a device for producing an object in the course of layer-by-layer material deposition on a construction platform.
A material reservoir 2, which has a container implemented having an open top and a floor 3 which is movable vertically upward step-by-step. The reservoir stores the material 1, which is typically provided in powder or granule form. Setting of the height of the container floor 3, results in a material layer 1′ having a predefined layer thickness protruding over an upper deposition plane 4, which directly adjoins the upper container opening of the material reservoir 2. With the aid of a stripping device 5, which is linearly movable from left to right in the exemplary embodiment shown according to FIG. 2, the material layer 1′ protruding beyond the deposition plane 4 is stripped off and pushed in the direction of motion of the stripping device 5 toward a construction platform 6 adjoining directly on the right. The construction platform 6 is also mounted so it can be vertically lowered, and is lowered in relation to the deposition plane 4 in such a manner that the material carried along by the stripping device 5 can be applied uniformly distributed in the layered construction space between the deposition plane 4 and the uppermost material layer already deposited on the construction platform 6. In the example shown, material already applied by preceding deposition procedures is located on the construction platform 6, which has solidified in specific layer areas. Various method techniques are known for the local solidification of the respective uppermost applied material layer. In the scope of so-called selective sintering, laser or electron beam sources are a chosen to treat the respective material which is used. The material deposited on the construction platform is slightly fused or melted locally, whereby a solid material layer results after cooling. In addition to the known irradiation technologies, which cause material solidification based on coagulative processes, chemical activators can also be applied locally to the uppermost material layer in the form of so-called binders by means of suitably implemented applicators, preferably in the form of inkjet print heads, whereby the powder or granule particles within the material layer stick to one another and produce a solid adhesive bond to the solidified material layers located underneath. Such a print head is provided with the reference 7 in FIG. 2, which can be deflected horizontally along the motion plane 4 over the uppermost material layer deposited on the construction platform 6. Solely for the sake of completeness, it should be noted that a catch container 8 is located to the right of the construction platform, into which the excess material is introduced by the stripping device 5, which is suitable for reuse.
The production of the most compact and homogeneously distributed possible material layers on the construction platform is of particular interest, which various tools can be used to implement. A stripping device 5 implemented as a rotating roller is illustrated for this purpose in FIG. 3a, which guides a material portion 9 of pre-definable size with it in the motion direction (see arrow illustration). The rotating roller is guided vertically spaced apart from the construction platform 6 or a material layer 10 already located thereon in such a manner that a uniform, “fresh” material layer 10′ forms directly following the roller in the motion direction. Through suitable distance setting between the roller-shaped stripping device 5 and the uppermost material layer 10 already applied to the construction platform 6, minimal layer thicknesses of approximately 100 μm can be generated. A blade-like stripping device 5 is illustrated in FIG. 3b, which is referred to as a squeegee or doctor blade. The material application is fundamentally performed in the area of the construction platform in the same way as in the above-described case of the illustration in FIG. 3a. 
The publication DE 198 53 978 C1 discloses a slide which is used to strip the material off of a material reservoir and is applied in layers onto a construction platform. In addition, the device has a grinding apparatus fastened rigidly in front of the slide in the form of a roller coated with grinding material. The surface of the process layer, that is the material, is melted by a laser and is smoothed before the further material application.
In addition, application methods are known which apply brushes, funnels, or screen techniques. These methods in all known cases only form slightly or inadequately pre-compacted or compacted material layers on the construction platform. As a result, even after the further application of radiant energy or chemical activators to solidify selective layer areas, so-called green parts having a green part density which is to be increased, results especially because parts produced in this way are typically subjected to further treatment steps. For example thermal curing processes are used, which can cause material shrinkage or shape warping, which is to be avoided, in particular in cases in which the objects are precision parts or parts from prosthetics.
U.S. Pat. No. 5,637,175 discloses a device for performing a manufacturing method, in which material is applied from a material reservoir, which is situated over a construction platform, to the construction platform. By moving the construction platform, the material layer is smoothed on a smoothing apparatus and subsequently compressed by means of a stationary roller or also a band guided over rollers.
The publication DE 10 2006 019 860 A1 relates to a manufacturing method for producing three-dimensional objects from a liquid construction material which can be solidified by light. Construction material is applied to a circulating band or to a film which moves back and forth and transferred therefrom with as few bubbles as possible to a substrate.